1. Field of the Invention
This invention pertains to the method used to produce that class of structural fit intended to prevent any relative movement between a pair of members wherein at least a portion of a first member is tightly lodged within an opening of complimentary configuration formed by and within a second member.
More specifically, this invention is directed to a chemically implemented assembly method for producing such structural fits and connections wherein precision pre-fitting of the members prior to assembly is not required, and hand or manual assembly can be done under field conditions, not requiring fixtures or presses.
2. Summary of the Prior Art
The most commonly used method of producing this class of fit is by precision machining a shaft member to be slightly larger in cross section than the precision machined complimentary opening into which it must be forced by mechanical pressure. This method is intensive in both skilled labor and equipment requirements, requiring as well the backup services of a good inspection department. When the reliability and quality of the structural connection warrants the relatively high cost, this method has generally been preferred.
Another method, generally reserved for larger diameter applications, that of thermal shrinkage fitting is commonly used. The outer member is heated to expand its dimension, and then very quickly assembled to the internal member which has been chilled or frozen. The members tend to occupy common space as their temperatures normalize.
Various clamping systems have been used to secure two telescoping parts together, typically, the hole member being split and drawn tightly around the shaft member by threaded means and a third clamping member. The connection so produced may offer certain advantages in terms of adjustability, ease of assembly and disassembly, and lowered costs, however the strength and reliability are also lowered with respect to that of joints produced by the previously described methods.
Alternatively, the shaft may be threaded and then drawn through the hole member and secured with a nut, or, both members may be threaded, assembled, adjusted, and secured with a jam nut. Such designs sometimes employ a mechanical key to provide resistance to torque loads or to disassembly.
Use of a mutually locking taper formed by the members at the joint interface, sometimes additionally secured by a threaded member, may provide a relatively strong and reliable connection, however the overall axial length of such an assembly may not be predetermined, due to the unknown makeup length required by the taper.
Of course, metallurgy permitting, the members may simply be brazed or welded together, however such a procedure tends to render future disassembly for repair, maintenance, or transportation either difficult, destructive, or impractical.
Other more elaborate devices, often resembling collet chucks, are intended to maintain torsional integrity and concentricity in power transmission equipment and the like.